The present invention relates to a method of polishing a work, more precisely relates to a method of polishing a work, which is capable of reducing load applied to a carrier and the work so as to precisely polish the work.
In a conventional apparatus for polishing both surfaces of a work, e.g., lapping apparatus, polishing apparatus, a work is held by a carrier, which engages with a sun gear and an internal gear and which is orbited around the sun gear. An upper polishing plate and a lower polishing plate, which are rotated in the opposite directions, respectively contact and polish both surfaces of the work. Abrading liquid (slurry) is fed while polishing the work. In a polishing apparatus, polishing pads are respectively adhered on polishing faces of upper and lower polishing plates. Note that, in the following description, the words “abrasion” and “lapping” fall into the concept of “polish”.
In the conventional polishing apparatus, the upper polishing plate and the lower polishing plates are rotated in the opposite directions. Further, an orbital direction and a speed of the carrier is adjusted so as to make a frictional force between the upper polishing plate and an upper face of the carrier and a frictional force between the lower polishing plate and a lower face of the carrier equal and orient in the opposite directions. However, the carrier is orbited and rotated, so influence of the rotation cannot be ignored. Thus, relative speeds between the polishing plates and the carrier are controlled on the basis of a prescribed formula considering the rotation of the carrier so as to reduce a load applied to the carrier (see Japanese Patent Gazette No. 5-123962).
However, in the method disclosed in the Japanese gazette, the work cannot be always precisely polished, in spite of the complex formula, due to various factors. Namely, the load applied to the carrier is influenced by not only the rotational speeds of the polishing plates, an orbital speed and the rotational speed of the carrier but also conditions of the polishing plates (polishing pads), amount of feeding abrasive liquid (slurry), etc. The conventional method does not consider those factors.